The proposed research is designed to develop and apply methods of replicating stomatic and restorative dental structures in vivo for analysis using scanning electron microscopy. The replicating materials used are developments of dental impression materials and replicating materials used in conventional electron microscopy. The replica method should simultaneously reproduce gross anatomy and ultrastructural detail. The replica methods developed in the first part of the investigation will be applied to study several problems of clinical dental interest. Etching and remineralization processes of enamel in vivo in dogs and in human patients will be studied and compared to similar processes occurring in vitro. Ultrastructural changes in vivo at the amalgam margins will be investigated to determine factors which lead to fractures of the amalgam margin. In all cases the SEM will be used for evaluation and characterization of changes occurring over extended time periods. Human subjects will not be used until year three of the proposed research program.